Hi, This is not really satisfactory:
-what about parallelism?
-what if you want to point to the circular object by giving it a name instead of just printing "repeated stuff here"
For the equality you will need that.
For equality of circular objects you even need problems like DFS minimization:
For example assume you have a Node=Struct.new(int,node)
is it the case that
start=Node(0,start)
is equal to
start=Node(0,Node(0,start))
? in certain interpreations of recursive equality it is the same, in other it is not.
Good points, although I don't think parallelism is relevant here. Of course if you mutate things while inspecting them you get odd results. This is the same for equality or any other operation.
About circular objects, the answer is: structs are passed as values, so they can't be circular by restriction, and a class (reference) would consider the two examples above to be different. If you want something smarter, you have to code it yourself. The motto here could be
``do simply what works most of the time and let the complex be easily incorporated too''
? are you talking about ruby here? Structs are definitively passed by reference.
Person = Struct.new(:name,:age,:friends) {
def inspect() to_s end
def to_s() "Person[#{name},#{age},#{friends}]" end
}
def methIn(person)
person.age=50
end
bob = Person["Bob",14,[]]
methIn(bob)
puts bob #prints Person[Bob,50,[]]
If they were passed by value then methIn would only be altering its local copy.
I do not think that anything at all is passed by value in ruby.
ok then... I'm interested in the gritty details of circular equality in ruby.
I also wrote on reddit (reddit.com/r/ruby/comments/syemrs/...) searching for a better answer, and I'm getting some, but I'm still confused.
You can also take a look at the way we are probably going to do it in Crystal (similar to Ruby, but you don't need to understand C): github.com/crystal-lang/crystal/is...
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Hi, This is not really satisfactory:
-what about parallelism?
-what if you want to point to the circular object by giving it a name instead of just printing "repeated stuff here"
For the equality you will need that.
For equality of circular objects you even need problems like DFS minimization:
For example assume you have a Node=Struct.new(int,node)
is it the case that
start=Node(0,start)
is equal to
start=Node(0,Node(0,start))
? in certain interpreations of recursive equality it is the same, in other it is not.
Good points, although I don't think parallelism is relevant here. Of course if you mutate things while inspecting them you get odd results. This is the same for equality or any other operation.
About circular objects, the answer is: structs are passed as values, so they can't be circular by restriction, and a class (reference) would consider the two examples above to be different. If you want something smarter, you have to code it yourself. The motto here could be
``do simply what works most of the time and let the complex be easily incorporated too''
? are you talking about ruby here? Structs are definitively passed by reference.
If they were passed by value then methIn would only be altering its local copy.
I do not think that anything at all is passed by value in ruby.
Sorry! I meant in Crystal.
ok then... I'm interested in the gritty details of circular equality in ruby.
I also wrote on reddit (reddit.com/r/ruby/comments/syemrs/...) searching for a better answer, and I'm getting some, but I'm still confused.
The way it works is:
What happens if these objects are compared in other threads at the same time? Well, the global table keeps these pairs per thread!
At least that's how it will work in Crystal (supporting recursive
to_sis done with a similar algorithm.)If that default equality isn't a good default, you can always override
==in Ruby and Crystal.You can also take a look at the way we are probably going to do it in Crystal (similar to Ruby, but you don't need to understand C): github.com/crystal-lang/crystal/is...